Gtk's detection problem with pkg-config

[alexandre schenberg]

Hi. While trying to build an old gimp version, I found a bunch of problems with Gimp's configure gtk detection code.
One of them is related to pkg-config. This line: " if $PKG_CONFIG --atleast-version $min_gtk_version $pkg_config_args;"
should evaluate to true. However, by some mysterious way, is not. But why? I checked the value of its variables:
 $PKG_CONFIG is equal to /usr/bin/pkg-config 
 $min_gtk_version is equal to 2.12.5
 $pkg_config_args is equal to gtk+-2.0 gthread-2.0

The first two are ok and the third seems ok at first glance

I am passing Gtk's pkgconfig config with: PKG_CONFIG_PATH=/media/34GB/Arquivos-de-Programas-Linux/Gtk+-2.24.20/lib/pkgconfig/: with is also okay.

So I would deeply appreciate if someone has any suggestions about the reason this if clause is failing to evaluate as true